Electrolytic process of bleaching and refining



B. S. & L. L. 'SUMMERS ELEGTROLYTIO PROCESS or BLBAGHING AND REPINING.4No:15.69.680.

Patented Oct. 20,l 1896.;

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@df/#2# 12e/f UNITED STATES PATENT OFFICE.

BERTRAND S. SUMMERS AND LELAND L. SUMMERS, OF CHICAGO, ILLINOIS.

ELECTROLYTIC PROCESS OF BLEACHING AND REFINING.

SPECIFICATION forming part of Letters Patent No. 569,680, dated October20, 1896.

Application filed November 29, 1895. Serial No. 570,394. (No specimens)To @ZZ 'Lz/'7mm it may concer/L.-

Be it known that we, BERTRAND S. SUM- MERS and LELAND L. SUMMEES,citizens of the United States, residing at Chicago, in the county ofCook and State of Illinois, have invented a certain new and usefulImprovement in Elcctrolytic Bleaching and Refining Processes, (Case No.2,) of which the following is a full, clear, concise, and exactdescription, reference being had to the accompanying drawings, forming apart of this specification.

Our invention relates to an electrolytic bleaching and refining process,the object of our invention being to provide an improved method ofbleaching and rening various fibers and materials employed in the artswithout impairin g the strength of the materials, and, furthermore, toprovide an improved process of degumming, bleaching, and

refining the vegetable fiber known in the arts as ramie or chinagrassVarious substances have been chemically employed heretofore forbleaching purposes, most notably chlorin, sulfur, and the caustics; butthese processes of bleaching are not satisfactory, as the bleachingagents thereof are so active that unless certain precautionary measuresbe adopted, entailing time and labor, the action is such as to affectthe strength of many fibers or materials, either by producing immediatedisintegration or by so impairing the strength that after a short lapseof time the fibers fall to pieces.

XVe have discovered that certain chemical agents, such as the commercialhydrates, will, when electrolyzed, yield bleaching agents at thepositive pole in a solution giving an alkaline reaction at the positivepole. The presence of the alkaline solution at the positive pole resultsin a very effective bleaching action, which, however, with certainfibers may produce a destructive action, and to prevent this certainagents may be used, which, however, may cause the production ofareaction at the positive pole neutral or even acid in character, as, forinstance, when a fluoride is added to the bath. TVe have employed sodiumfluoride, potassium fluoride, and cryolite. By varying the strength ofthe current a reaction, resulting in either an acid or an alkalinesolution at the positive pole, may be produced, and this result isobtained even when the quantity of fiuoride is small as compared withthe quantity of hydrate. In practice the quantity of each and thestrength of the current are so proportioned as to maintain theA -acidreaction at the positive pole.

le have successfully employed various of the alkaline hydrates forbleaching purposes after the manner of our invention,v but in practicepreferably employ sodium hydrate upon the material to be bleached, andto pre-v vent this we add a fluoride to the bath, as above described.

The solution of the hydrate is placed inthe electrolytic cell and thepositive and negative electrodes are immersed in the solution, thematerial to be bleached being immersed in the solution in the vicinityof the positive pole. A porous partition or diaphragm is interposedbetween the two electrodes, which for best results should benon-permeable to diffusive action, while readily pervious to theelectrolytic action. The solutions resulting from the electrolyticaction are thus confined to their respective poles, and the solutionpresent at the negative pole is thus prevented from coming in contactwith the material to be bleached, and thereby diminishing the desiredelectrochemical action upon the material to be bleached, which isimmersed in the solution at the positive pole. The bleaching process asthus practiced is very active, and the time during which the material issubjected to the bleaching process must be carefully determined, as toolong a subjection to the bleaching process may affect the material. Wehave discovered, however, that if a iiuoride solution be added to thehydrate bath the tendency to affect the strength of the material onextended or continued subjection of the material to the bleachingprocess is removed, the fluoride possessing the property ofcounteracting the destructive effect of the bleaching agents. Thequantity of the fluoride need not be great and maybe determined for theparticular material to be bleached by experiment.

The process, as above described, is adapted for the bleaching of any ofthe materials, such IOO as pulps, cloths, theanimal and vegetablefibers, and, in fact, any of they substances that are usually bleachedin the arts, and is particularly applicable to those materials thefibers of which are easily attacked and are either destroyed or impairedby such bleaching agents as are commonly used in the arts.

We are aware that caustic potash and caustic soda have been employed forchemically bleaching materials, the`bleaching being due to the directchemical action of the hydrate on the coloring-matter; but by thepresent electrolytic process itis not the hydrate in itself that effectsthe bleaching process, but the products liberated therefrom by theelectrolytic action, and we find that the same hydrates have a verydifferent effect when employed for electrolytic bleaching from thatwhich they have when employed for chemical bleaching.

l/Ve find our process particularly adapted to the preparation of thefibers of'k ramie or china grass, which possess a remarkable strengthwhen properly prepared, but which -are very susceptible to the action ofbleaching agents and are readily weaken ed thereby. Some bleachingagents have the effect of immediately destroying the fibers, whileothers so im pair them in strength that after the lapse of a short timethey disintegrate and fall to pieces.

In an application filed by Bertrand S. Summers and Charles O. BoringNovember 4,-

1895, Serial No. 567,847, an electrolytic process of removing the gumsand cementing material from the fibers of ramie and other vegetablefibers is described, according to which process the fibers are subjectedto the action of a fiuoride bath.

We find that` by the employment ofthe bleaching process of the presentinvention in connection with the degumming process of theabove-mentioned application a better product can be secured than by theemployment of the said degumming process alone. In practicing theinvention we may first subject the ramie fibers to the hydrate bath,

which also has the property of removing a large proportion of the gumVor cementing material, the fibers being thus separated and bleached.After the fibers have been subjected to the hydrate bath they may beremoved and immersed in the fluoride bath and the process completed. Itis preferable when the invention is thus practiced in separate baths toplace a small quantity of the fluoride solution in the hydrate bath inorder that the fibers may not be impaired in strength by the action ofthe bleaching agents.

When the fibers are removed from the hydrate bath, it will be found thatthey are somewhat harsh, and not soft and delicate, as is desirable.After placing in the fiuoride bath, however, the harshness will be foundto be completely removed, the fluoride bath, when employed with thehydrate bath, serving to refine the fibers, either by the further andcomplete removal of the gum or cementing material 'or by the removal ofthe silica or other substances which may remain in the fibers.

Instead of employing separate hydrate and uoride baths the two may becombined, and instead of adding only sufficient fluoride solution to thehydrate bath to prevent the destruction of the fibers during thebleaching process a sufficientquantity of the fluoride may be added toeect the complete refining and softening of the fibers, the completeprocess of degumming, bleaching, and refining the fibers being thuseffected in the single bath. XVe prefer, however, to employ separatehydrate and fluoride baths, as better results are obtained thereby.

We have illustrated the apparatus for practicing our invention in theaccompanying drawings, in which- Figure l is a view of an experimentalapparatus which we have employed for bleaching purposes. Fig. 2 is aview of apparatus which we have employed for the refining process. Fig.3 is a view of apparatus as designed for practical use.

Like letters refer to like parts in the several figures.

Within a jar or retaining vessel ct is supported a porous vcup b. Withinthe cup b, having an opening b3 in the bottom to lower the electricalresistance of the bath and to maintain the level of the liquid the sameupon the inside and the outside of the cup, is supported a partition h',beneath which is the positive electrode c, the negative electrode CZbeing immersed in the solution upon the eX- terior of the porous cup.The positive and negative electrodes are connected with a source ofelectricity e, and the electrodes are immersed in the bleachingsolution, in practice a solution of sodium hydrate. terial to bebleached is supported upon the shelf Z9 or maintained in an immersedposition in any convenient manner in the solution within the porous cup.Vhen current is passed through the cell, the bleaching agents areliberated at the positive pole, and thus come in contact with and actupon the material to be bleached.

In Fig. 2 we have illustrated a cell similar in all structural detailsto that illustrated in Fig. l, and this cell may be employed for therefining process, a liuoride bath being provided in the cell, to theaction of which the fibers are subjected.

In Fig. 3 we have illustrated a vat ct', divided into two compartmentsby a porous partition b2, the positive electrode c being in the form ofa large plate occupying a horizontal position, upon which the materialto be bleached may be laid or in the vicinity of which it may besuspended. A number of negative electrodes d d are provided upon IOO IIO

the opposite side of the partition b2, the elec- Having described ourinvention, what we claim as new, and desire to secure by Letters Patent,is-

l. The herein-described method of bleaching, which consists in immersingthe material to be bleached in the region of the positive pole in anelectrolytic bath containing a hydrate and a fluoride, passing a currentof electricity through said bath, and isolating the chemical agentspassing to the positive pole which come in contact With the material tobe bleached from the agents passing to the negative pole, substantiallyas described.

2. The herein-described method of bleaching by which the deleteriouseffects of the bleaching agent are prevented, which consists inimmersing the material to be bleached in an electrolytic bath containinga fluoride and a materia-l yielding a bleaching agent when electrolyzed,and passing a current of electricity through saidl bath, whereby thefluoride acts to prevent deleterious action upon the material beingbleached, substantially as described.

3. The herein-described process of degumming, bleaching and refiningvegetable fibers iniiuence of a bath con taining sodium hydrate and asmall quantity of a fluoride, passing a current of electricity throughsaid bath, and then subjecting the iibers to the influence of a fluoridebath, and passing a current of electricity through said bath;substantially as described.

In Witness whereof we hereunto subscribe our names this 22d day ofNovember, A. D.

BERTRAND S. SUMMERS. LELAND L. SUMMERS.

lVitnesses:

W. CLYDE JoNns, GEORGE L. GRAGG.

